﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Drawing;
using System.Windows.Forms.VisualStyles;

namespace System.Windows.Forms;

/// <summary>
///  This is a rendering class for the ScrollBar control.
/// </summary>
public static class ScrollBarRenderer
{
    // Make this per-thread, so that different threads can safely use these methods.
    [ThreadStatic]
    private static VisualStyleRenderer? t_visualStyleRenderer;

    /// <summary>
    ///  Returns true if this class is supported for the current OS and user/application settings,
    ///  otherwise returns false.
    /// </summary>
    public static bool IsSupported => VisualStyleRenderer.IsSupported; // no downlevel support

    /// <summary>
    ///  Renders a ScrollBar arrow button.
    /// </summary>
    public static void DrawArrowButton(Graphics g, Rectangle bounds, ScrollBarArrowButtonState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.ArrowButton.LeftNormal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a horizontal ScrollBar thumb.
    /// </summary>
    public static void DrawHorizontalThumb(Graphics g, Rectangle bounds, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.ThumbButtonHorizontal.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a vertical ScrollBar thumb.
    /// </summary>
    public static void DrawVerticalThumb(Graphics g, Rectangle bounds, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.ThumbButtonVertical.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a horizontal ScrollBar thumb grip.
    /// </summary>
    public static void DrawHorizontalThumbGrip(Graphics g, Rectangle bounds, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.GripperHorizontal.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a vertical ScrollBar thumb grip.
    /// </summary>
    public static void DrawVerticalThumbGrip(Graphics g, Rectangle bounds, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.GripperVertical.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a horizontal ScrollBar thumb.
    /// </summary>
    public static void DrawRightHorizontalTrack(Graphics g, Rectangle bounds, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.RightTrackHorizontal.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a horizontal ScrollBar thumb.
    /// </summary>
    public static void DrawLeftHorizontalTrack(Graphics g, Rectangle bounds, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.LeftTrackHorizontal.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a vertical ScrollBar thumb in the center of the given bounds.
    /// </summary>
    public static void DrawUpperVerticalTrack(Graphics g, Rectangle bounds, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.UpperTrackVertical.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a vertical ScrollBar thumb in the center of the given bounds.
    /// </summary>
    public static void DrawLowerVerticalTrack(Graphics g, Rectangle bounds, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.LowerTrackVertical.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a ScrollBar size box in the center of the given bounds.
    /// </summary>
    public static void DrawSizeBox(Graphics g, Rectangle bounds, ScrollBarSizeBoxState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.SizeBox.LeftAlign, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Returns the size of the ScrollBar thumb grip.
    /// </summary>
    public static Size GetThumbGripSize(Graphics g, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.GripperHorizontal.Normal, (int)state);

        return t_visualStyleRenderer.GetPartSize(g, ThemeSizeType.True);
    }

    /// <summary>
    ///  Returns the size of the ScrollBar size box.
    /// </summary>
    public static Size GetSizeBoxSize(Graphics g, ScrollBarState state)
    {
        InitializeRenderer(VisualStyleElement.ScrollBar.SizeBox.LeftAlign, (int)state);

        return t_visualStyleRenderer.GetPartSize(g, ThemeSizeType.True);
    }

    [MemberNotNull(nameof(t_visualStyleRenderer))]
    private static void InitializeRenderer(VisualStyleElement element, int state)
    {
        if (t_visualStyleRenderer is null)
        {
            t_visualStyleRenderer = new VisualStyleRenderer(element.ClassName, element.Part, state);
        }
        else
        {
            t_visualStyleRenderer.SetParameters(element.ClassName, element.Part, state);
        }
    }
}
